Foreign ministers from Germany and Luxembourg are set to meet their counterparts from the Czech Republic, Hungary, Poland, and Slovakia in Prague for talks on a controversial system to distribute 160,000 new arrivals around the bloc.

The Baltic states rejected the quotas last week, saying the EU should focus on tackling the root causes of the migrant crisis, protecting the borders of the passport-free Schengen area and fighting migrant smugglers.

But Germany, which is spearheading Europe's response to the emergency, said the plan put forward by European Commission chief Jean-Claude Juncker would still not be enough to deal with the biggest migrant crisis since World War II.

"The distribution of 160,000 refugees across Europe is a first step, if one wants to be polite," said Deputy Chancellor Sigmar Gabriel. "It's a drop in the ocean."

On Europe's eastern borders the scale of the crisis was clear as record numbers of migrants streamed through the Balkans into Hungary on Thursday, braving police truncheons and torrential rain in their desperate attempt to reach Western Europe.

The surge in arrivals, which Hungarian police said saw 3,321 people enter the country in just 24 hours, forced Austria's train operator to suspend services with Hungary due to "massive overcrowding".

Many are hurrying to cross the border before Hungary brings in tough new anti-migrant laws on September 15 -- a move strongly criticised by the UN's refugee agency, which on Tuesday predicted 42,000 migrants will enter the country by next week.

Others, fleeing war and poverty in the Middle East, Afghanistan or Pakistan, have endured treacherous and often deadly sea journeys across the Mediterranean to reach European soil.

Some 22,500 refugees and migrants on the Greek island of Lesbos have been registered by officials since Monday evening, according to police, many of them Syrian refugees setting sail from Turkey.

Migrant walk through rain from Roszke to Szeged in Hungary Thomson Reuters

'An accountancy exercise'

The European Union is bitterly divided over how to cope with the biggest migrant crisis in seven decades, with transit countries on the front line taking a tough stance while Western Europe has thrown open its doors.

Under the plan unveiled this week, Germany would take more than 31,000 migrants, France 24,000 and Spain almost 15,000. Britain has separately pledged to take 20,000 Syrians from refugee camps outside the EU over five years.

Hungary has stirred anger with its heavy-handed tactics including building a fence along its border with Serbia patrolled by sniffer dogs and possibly the army -- but its stance on quotas was echoed by its neighbours.

"It is inappropriate to talk about mandatory quotas, calculated on an extremely bureaucratic basis, almost like an accountancy exercise I might say, without consulting member states," said Romania President Klaus Iohannis.

His views echoed those of Slovakian Prime Minister Robert Fico, who said Wednesday he did not "want to wake up one day and have 50,000 people here about whom we know nothing".

Juncker's proposals include a possible revision of the EU's much-criticised Dublin Treaty, under which asylum claims must be processed by the first country where refugees arrive.

EU lawmakers called for an international conference on migration bringing together the United States, United Nations and Arab countries.

Refugees wait on a platform for a train at the Keleti train station in Budapest, Hungary, September 3, 2015 Leonhard Foeger/Reuters

'Walking for hours'

Facing criticism that his government has been too slow to help, US President Barack Obama pledged to admit at least 10,000 Syrian refugees in the year starting October 1.

Spokesman Josh Earnest said Obama had ordered staff to "scale up" the number of Syrian refugee admissions from around 1,500 this year after over 62,000 Americans signed a petition calling on Washington to take in more people.

Meanwhile, on the Greek island of Lesbos, another flashpoint in Europe's crisis, the boats kept arriving.

Hundreds -- perhaps thousands -- made a gruelling 50-60 kilometre (30-40 miles) walk from their landing place to the main town where they must go to receive registration papers.

"We have been walking for four hours. There is no bus, no taxi, no water, no anything," said Mohammed Yassin al-Jahabra, a 23-year-old English literature student.

Thousands of people have been forced to camp on the streets in squalid conditions, and there were repeated clashes as riot police struggled to control huge crowds pressing forward to get on board ferries.

But the boats are still arriving at an astonishing pace, with six landing in the space of an hour on Wednesday.